The present invention relates to a rubber composition for covering a carcass cord and a tire having a carcass using the rubber composition.
Since big load is generally applied to tires for an automobile, a carcass cord is used as a reinforcing material. In particular, when the carcass cord is peeled from a rubber due to heat generation in tires during running, it causes a fatal tire trouble.
Raw materials derived from petroleum resources such as carbon black have been used for a rubber composition for covering a carcass cord. However, in recent years, there has been an increasing interest in global environmental conservation and there is no exception in automobiles, and regulations on CO2 emission has been made more rigorous. Further, petroleum resources are finite and its supply quantity has been decreasing year by year. Therefore, a steep rise of petroleum price is anticipated in future and there is a limit in using raw materials such as carbon black and synthetic rubbers derived from petroleum resources. Therefore, considering petroleum depletion in future, it is necessary to use non-petroleum resources such as a natural rubber and white fillers such as silica and calcium carbonate. However, in such a case, there is required reinforcing property such as rubber strength equal to or better than that of a conventional rubber composition using petroleum resources as main component.
As a method of reducing rolling resistance, a method of using silica which is a raw material derived from resources other than petroleum has been known (refer to JP2003-63206A). When silica is compounded, rolling resistance is reduced, and also a ratio of raw materials derived from petroleum resources can be reduced, thereby making it possible to consider an effect on environment and prepare for decrease in supply quantity of petroleum in future. However, reduction of rolling resistance is not sufficient, and rubber strength is not superior to that of a tire produced by using raw materials derived from petroleum resources as main component. Therefore, improvements are still required in either of performances.